The invention relates to an evaporation system for separating a fluid mixture into its component parts, especially for the purpose of solvent reclamation, wherein a vacuum pump is connected to an evaporator, especially a rotation evaporator, and also at least one solvent separator on the suction side of the vacuum pump and at least one secondary condenser on the pressure side of the vacuum pump are attached.
Solvents are often used as adjuvant substances in chemical laboratories and, for example, are required for the synthesis of new substances. In the past, the reclamation of solvents has been considered a minor issue. As a result of the change in environmental consciousness with regard to emissions, and also the increased awareness of danger and cost to the user, re-orientation of this viewpoint has only occurred over the last few years. Hence, vacuum systems for the reclamation of solvents have been developed in the past few years which are geared towards the optimization of these three points.
In order to be able to reclaim the solvent, it is already known, for example, to heat the solvent in a rotation evaporator over a water bed. For evaporation of the solvent, pressure and temperature must be coordinated with one another, since every solvent has a boiling pressure at a certain temperature at which it evaporates. The boiling pressure in the rotation evaporator is generated by the vacuum pump. Initially, when commencing evaporation of the solvent, the glass flask of the rotation evaporator is at atmospheric pressure. Then, the vacuum pump also evacuates the boiling pressure which results from the respective bath temperature. When this pressure is reached, the solvent begins to evaporate from the original fluid mixture. The boiling pressure should then be kept constant.
It is already known to provide a fine regulating valve with foreign gas feeding for this purpose. Upon reaching the boiling pressure, the fine regulating valve is opened far enough for the boiling pressure to be kept constant by the influx of foreign gas, generally air. Later in the process, the vaporous solvent is to condense on the cooling coil in the rotary evaporator, drain off and be collected in the evaporator's round flask. However, a part of the vapor escapes from the rotary evaporator through the vacuum pump, and then condenses under atmospheric pressure in a water-cooled secondary condenser.
With these known systems, the following problems have resulted in practice:
In the case of solvents with a low boiling point, the utilized vacuum pumps have too great a suction capacity, meaning that a correspondingly high gas speed results. This presents the danger of a large quantity of the solvent being pulled along still in a fluid state, whereupon it would not be able to condense in the rotary evaporator. The high gas speeds also occur in the secondary condenser, where they also prevent efficient condensation, so that the solvent vapor can also escape out into the surrounding air.
Another disadvantage is that the solvent condensing in the round flask of the secondary condenser cannot be reused, as it is contaminated, for example by the plasticizers in the connecting pipes. This part of the reclaimed solvent must therefore be discarded.
It is also already known to dispose an electromechanical vacuum valve, controlled by a vacuum controller, in the connecting pipe between the rotation evaporator and the membrane pump. The pressure in the rotation evaporator is measured via the vacuum controller, and the vacuum valve is closed when boiling pressure is reached. The vacuum pump evacuates the connection pipe between the vacuum valve and the pump to the final pressure of the pump. The vacuum valve must be opened from time to time, so that the pump can again evacuate to the boiling pressure of the solvent which is to be evaporated. A rapid pressure increase or pressure equalization in the connection pipe to the rotation evaporator results from the sudden opening of the vacuum valve. As a result, the pressure in the connection pipe to the pump also increases, and with the pressure, also the suction capacity of the pump. Likewise, the flow speed throughout the system increases in proportion to the suction capacity. The aforementioned disadvantages result from this. Furthermore, a vacuum controller and the vacuum valve are expensive, meaning that the system as a whole is expensive to purchase.